NASA’s rover Opportunity this week began its 15th year on the surface of Mars, but scientists at the Jet Propulsion Laboratory in Pasadena say they currently can’t raise the craft.

The rover landed in a region of the Red Planet called Meridiani Planum on Jan. 24, 2004, sending its first signal back to Earth from the surface in the first minutes of Jan. 25, recalled a JPL statement.

The golf-cart-sized rover was designed to travel 1,100 yards and operate on the Red Planet for 90 Martian days. It has traveled over 28 miles and logged its 5,000th Martian day back in February of 2018, according to the statement.

“Fifteen years on the surface of Mars is testament not only to a magnificent machine of exploration but the dedicated and talented team behind it that has allowed us to expand our discovery space of the Red Planet,” said John Callas, project manager for Opportunity at NASA’s Jet Propulsion Laboratory.

“However, this anniversary cannot help but be a little bittersweet as at present we don’t know the rover’s status. We are doing everything in our power to communicate with Opportunity, but as time goes on, the probability of a successful contact with the rover continues to diminish.”

Opportunity’s last communication with Earth was received June 10, 2018, as a planet-wide dust storm blanketed the solar-powered rover’s location on the western rim of Perseverance Valley, eventually blocking out so much sunlight that the rover could no longer charge its batteries, the statement said.

Although the storm eventually abated and the skies over Perseverance cleared, the rover has not communicated with Earth since then. However, Opportunity’s mission continues, in a phase where mission engineers at JPL are sending commands to the rover and listening for its signals. If engineers hear from the rover, they could attempt a recovery.

Opportunity and its twin rover, Spirit, launched from Cape Canaveral, Florida, in 2003. Spirit landed on Mars in 2004, and its mission ended in 2011.